1. Field of the Invention
The present invention relates to a drive mechanism for the focusing of a microscope and more particularly to such a drive mechanism in which manual adjustments are made with a gear drive, and an additional fine adjustment is made by a motor through a control element.
2. Discussion of Related Art
A motor drive for the sharp focusing of microscopes with coarse and fine adjustments is disclosed in DE-P No. 22 62 612. The coarse and fine adjustments are effected by use of a common spindle, with the drive for the fine focusing being engageable and disengageable with the spindle. Two bidirectional motors are provided, one of which performs the coarse adjustment and the other of which performs the fine adjustment. A control element effects the engagement of the drive means with the fine adjustment motor by means of a cam and also controls the starting and stopping of the motors. The coarse adjustment motor has a shaft parallel to the spindle. A gear is mounted on this shaft and constantly meshes with a gear mounted on the spindle. The fine adjustment motor is supported on a carrier with its shaft perpendicular to the spindle. The carrier is pivotable against the tension of a spring. The fine adjustment motor shaft carries a worm, which meshes with a worm wheel seated on the spindle.
A coarse and fine focusing device is disclosed in JA No. 41-9420 which may be operated both manually and with a motor. The arrangement requires no coupling, but needs an additional gear drive for the motor. Furthermore, a vertical adjustment of the control knobs for manual focusing takes place simultaneously with the actuation of the drive.
In FR No. 1 316 033, a focusing mechanism for a microscope is disclosed which may be actuated manually and by means of a motor. Two separate drive shafts, acting on separate guides, for the manual coarse and fine adjustment are connected through two friction clutches and flexible shafts with two motors, which effect the coarse and fine motor focusing. Here again the adjusting knob for fine focusing travels upward or downward upon the actuation of the coarse adjustment.
Finally, DE-OS 26 27 486 discloses a coarse and fine adjusting gear drive for microscopes which may be actuated manually by means of a planetary gear drive or by a drive motor for automatic focusing. The automatic focusing is independent of the manual fine focusing by way of the planetary gear, but is effected through the same gear connection as the coarse drive motion and requires a further helical gear and an additional angular lever. The manual coarse and fine adjustments in this known apparatus require separate, parallel drive shafts.